This invention relates to a practically nonreflective and limitatively light-transmitting board which is particularly suitable for use as a front cover of a vehicle instrument panel.
In automobile instrument panels, for example, a front cover plate installed in front of the meters or display panels must be transparent enough to allow the driver to clearly read the meters or displays by natural light. For good readability through the cover plate, reflection of intense extraneous light from the cover plate and reflection of any equipment of the driver or passenger compartment on the cover plate are undesirable. Furthermore, while the meters or displays are illuminated or are emitting light as is usual at night, diffusion of light from the instrument panel into a side window is obstructive to the driver's looksee at a door mirror, for example.
It is conceivable to provide the transparent cover plate with an antireflective and anti-interferential coating film. In theory it is possible to produce an effective antireflective and anti-interferential coating film with respect to light of specific wavelengths within a narrow range. In practice, however, it is very difficult to fully accomplish the object with respect to natural light which is very wide in the range of wavelengths.